Type a word that is already on the board, for example CARE. Wortfinder shows you straight away which letters you can add in front or at the end (here S for SCARE, or D, R and S for CARED, CARER and CARES), and every longer word that contains it. Add your own tiles too and you only see extensions you can actually play, with points.
Scrabble players call these letters hooks: with a single tile you turn your opponent's word into a new one and score it again. More tools: the Scrabble word finder for your letters and the pattern search for gaps on the board.
Type the word that is on the board. Under “Fits in front” and “Fits at the end” you see every letter that makes a new valid word. If it says “nothing”, the word cannot be extended by one letter.
Yes. The list below the hooks shows every longer word that contains your word. If you enter your tiles, only the ones you can make with them stay, the highest-scoring at the top.
When you extend a word, the whole new word scores, including the tiles that were already there. If your new letter lands on a premium square, it is worth even more.